This invention relates to a process for the manufacture of O-silyl O,N-ketene acetals (SNKA), 1-organosiloxy-1-diorganoamino-2,2-diorganoethylenes. More specifically, this invention relates to a process for producing O-silyl O,N-ketene acetals from the reaction of alpha-haloamides with an alkali metal in the presence of excess organohalosilane.
For the purposes of the instant invention the term "O-silyl O,N-ketene acetal" refers to compounds of the general formula, EQU R.sub.2 C.dbd.C(OSiR.sub.n X.sub.3-n)(NR.sup.a.sub.2),
wherein each R and each R.sup.a is independently selected from a group consisting of alkyl, alkenyl, aryl, or aralkyl; X is a fluorine, chlorine, or bromine atom; and n is an integer from 1 to 3.
These compounds are of value becaue of their utility in the preparation of organic compunds which would be difficult to synthesize by other means. Another recent application is the use of the SNKA as acrylate polymerization initiators. This concept known as Group Transfer Polymerization (GTP) was developed by DuPont and is disclosed in three U.S. patents--U.S. Pat. No. 4,414,372, Farnham et al., issued Nov. 8, 1983; U.S. Pat. No. 4,417,034, Webster, issued Nov. 22, 1983; and U.S. Pat. No. 4,508,880, Webster, issued Apr. 2, 1985.
A primary means for preparing materials similar to SNKA cited in the art is the reaction of metalated amide enolate ions with organohalosilanes. Woodbury et al., J. Org. Chem., 1978, 43, pp. 881-884, describes the reaction of lithium N,N-dialkylamide enolates with trialkylchlorosilanes. The lithium amide enolates are prepared via the reaction of the appropriate amide with tetrahydrofuran solutions of lithium diisopropylamide. The solutions are then treated with a slight excess of the trialkylchlorosilane. Mahalanabis et al., Tetrahedron Letters, 1982, 23, pp. 3971-3974, describes the preparation of a compound with a similar structure to an SKNA via the reaction of an N,N-dialkyl succinamide with lithium diisopropyl amide, followed by quenching with trimethylchlorosilane. Green et al., Tetrahedron Letters, 1986, 27, pp. 535-538, discloses the preparation of structure similar to an SNKA via the reaction of a senecioamide with lithium diisopropylamide followed by treatment with trimethylchlorosilane.
A second route to compounds with structures similar to SNKA is the interaction of ketene with silylated amines. This route is described by Lutsenko et al., J. Organometal. Chem., 1969, 17, pp. 241-62.
Nowhere does the above art demonstrate or suggest the preparation of O-silyl O,N-ketene acetals from the reaction of an alpha-haloamide with an alkali metal in the presence of an excess of an organohalosilane.